Organic light-emitting diode (OLED) has advantage such as self-emission, quick-response, wide view-angle, high brightness, low weight, low thickness, flexibility, etc., so its marketing development is expected and OLED becomes the mainly developed display technique in the next generation.
According to the light emission mechanism, the OLED display device can be classified as the bottom emission type and the top emission type. The light of the top emission OLED display device is emitted from the top, and such device structure can largely improve the aperture ratio of the display panel. The top emission OLED display device generally utilizes reflective metal bottom electrode and transparent or semi-transparent upper electrode. The transparent electrode is conventionally conductive metal oxide, but its high energy manufacture process damage to the organic layer and is harmful for keeping the device functionality. The semi-transparent upper electrode is conventionally thin metal layer, and the thin metal layer has thickness between 10 nm and 15 nm for keeping its conductivity. The thin metal layer with such thickness has certain light reflectivity and results in the micro-cavity effect. Because the brightness of the micro-cavity structure varies with the view angle, one next to the OLED display device cannot see the display contents and the privacy of the display contents is ensured. However, it results in the problem of view angle and harmful for keeping the display effect of the OLED display device. That is, the display contents of the OLED display device cannot be dearly seen in arbitrary angle.